effect

protocol

Data name

Representative equipment

Define codec format, decompression, encryption and decryption

Establish, manage, and terminate sessions between communicating parties

Establish, maintain, and cancel an end-to-end data transmission process, reliable transmission (complete) and flow control (speed)

tcp, udp

segment segment

firewall

addressing, addressing, routing

ip, arp, ICMP, ospf

packet package

Routers, layer 3 switches

Encapsulation, framing, error detection

vlan, ethernet, ppp, PPPoE, stp, ISIS

frame frame

Layer 2 switches, network cards

transmit bitstream

bit bit

Hubs, repeaters, cables

It is a series of standards for network communication.

Make it easier for us to learn

= step by step

ISO-International Organization for Standardization

Because osi has a more detailed network structure and better theoretical design, it allows us to understand the network in more detail.

To explain by sending an email, first edit the email at the application layer and then send it to the presentation layer. The presentation layer can encrypt and compress the email and then pass it to the session layer. At this time, the session layer will start the email. This message is fed back to you and sent to the transport layer. The transport layer segments the message. Because the data cannot be transmitted at once, it needs to be segmented [so it is called message segments], and then sends the segmented data to the network layer. This When the network layer encapsulates the segments and adds headers to form data packets, it also selects a transmission path to transmit the data, and then passes the data packets to the data link layer. The data link layer adds headers and trailers and encapsulates them into frames. , and finally the frame is sent to the physical layer to form a bit stream

The session layer is equivalent to the leader telling the transport layer to establish a connection, and the transport layer rushes to establish the connection.